The present invention refers to a pantographic device for conveying loads in vehicle assembly lines and more specifically for conveying the vehicles or parts thereof along an assembly chain.
In vehicle assembly chains, it is currently necessary to convey loads through different work areas or posts where the assembly thereof is to be performed. Said loads can be formed by any of the vehicle components to be assembled, such as the chassis, engines, doors, etc.
To aid in the assembly tasks, it is helpful that the different vehicle components pass through the work stations or posts in a more or less elevated position, depending on the assembly tasks to be performed in each one of said work stations or posts.
Different devices for conveying loads in vehicle assembly lines are currently known, said devices generally having an elevated guide rail upon which a carriage is assembled which moves longitudinally along the guide rail in order to longitudinally shift the load in question or through the assembly line.
These devices also have a series of elements suspended from the shiftable carriage and which permit vertically shifting the load, distancing it from the ground in a greater or lesser degree.
In patent U.S. Ser. No. 09/986,097 from the same applicant, these elements intended to change the height of the load with regard to the ground include an upper frame assembled on the shiftable carriage, a lower frame provided with arms for holding the load and a lifting mechanism which enables changing the distance between the upper frame and the lower frame.
In said patent U.S. Ser. No. 09/986,097 from the same applicant, the upper frame and the lower frame are joined by articulated arms whose ends are respectively fixed to said upper frame and to said lower frame by means of horizontal rotation shafts.
In order to vertically shift the lower frame with regard to the upper frame, a rotating drum is assembled on said upper frame, which is actuated by a single motor member and which acts on cables fixed to the lower frame, such that when the cables wind and unwind in said rotating drum, the lower frame is lifted and lowered, respectively.
The use of a rotating drum actuated by a single motor element for causing the cables to wind and unwind, and the subsequent lifting and lowering of the lower frame, poses several drawbacks, among which it is worth mentioning the high maintenance costs of the rotating drum in order to ensure proper functioning thereof, periodic maintenance and revision of the cables, which increases the facility maintenance costs, and the risk of the lower frame lowering uncontrollably in the case that the motor element responsible for actuating the drum should experience a breakdown.